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I. Cox, S. MacRae, J. Porter, G. Yoon, C. Roberts, D. Williams; What Causes The Increase in Higher Order Aberrations After LASIK? The Cut, The Flap Manipulation and/or the Ablation? . Invest. Ophthalmol. Vis. Sci. 2004;45(13):211.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To understand individual effects of the microkeratome cut, mechanical lifting of the cut flap, and laser ablation on the resultant lower and higher order aberration (HOA) pattern after LASIK. Methods:A prospective study examined outcomes after the corneal lamellar resection, lifting of the flap and LASIK ablation. One eye each of 17 patients underwent microkeratome resection only. Ten eyes underwent lifting of the flap and sham ablation (flap lift group). In 7 eyes the flap was cut but not lifted (no flap lift group) followed by sham ablation. Aberrometry, topography, VA and refraction were performed preoperatively, and 20 minutes, 1 day, 1 week, 1 month and 2 months post–flap creation. At two months, eyes underwent ablation, conventional LASIK in the contralateral eye, and follow–up at 1 day, 1 week, 1 month and 3 months post ablation. Results:At 2 months post flap creation, the increase in HOA was 0% in the no flap lift group vs. 30% for the flap lift group; this was significant (p < 0.05). Furthermore, a small but significant increase in spherical aberration was observed in the flap lift group. 3 months following laser ablation, an increase in spherical aberration was observed in both groups (p < 0.05) proportionate to the amount of sphere corrected. Conclusions:Creation of the flap via microkeratome does not increase HOA; lifting the flap increases HOA by approximately 30%. Conventional laser ablation further increases HOA especially spherical aberration, proportionate to the amount of sphere corrected (Porter et al, AJO Sept 2003). Further studies on the mechanics of flap lifting and manipulation seem warranted.
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